On 20030203 (Mon) at 1117:44 -0800, Andrew Morton wrote:
> hum.
>
> So you have an operation which takes 30 seconds and generates 30 megabytes of
> dirty data. My wild guess would be that the first five seconds' worth of
> data are splattered all over the disk, and that the holes in that write
> pattern are filled in later in the run.
>
> So if a filesystem happens to decide to write the data after the first five
> seconds, there is little request merging. But if the filesystem were to wait
> the whole thirty seconds then voila - all the holes are filled in and there's
> a lot of request merging.
>
> Well. It's a theory. If you mount your data=ordered fs with `-o commit=60',
> what happens?
Recalling the times reported yesterday, in writeback it's 4 minutes and
change; data=ordered, roughly 27 minutes; the commit=60 result is about
the same as commit=5, as follows:
# umount /xtrn
# mount -t ext3 -o data=ordered,commit=60 /dev/sdc1 /xtrn
# time bogofilter -v -s -d /xtrn/db <spam_corpus
# 5898549 words, 14600 messages
real 28m9.866s
user 2m30.750s
sys 0m46.700s
--
| G r e g L o u i s | gpg public key: |
| http://www.bgl.nu/~glouis | finger greg bgl nu |
| Help free our mailboxes. Include |
| http://wecanstopspam.org in your signature. |